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- 'use strict';
- var aCallable = require('../internals/a-callable');
- var toObject = require('../internals/to-object');
- var IndexedObject = require('../internals/indexed-object');
- var lengthOfArrayLike = require('../internals/length-of-array-like');
-
- var $TypeError = TypeError;
-
- var REDUCE_EMPTY = 'Reduce of empty array with no initial value';
-
- // `Array.prototype.{ reduce, reduceRight }` methods implementation
- var createMethod = function (IS_RIGHT) {
- return function (that, callbackfn, argumentsLength, memo) {
- var O = toObject(that);
- var self = IndexedObject(O);
- var length = lengthOfArrayLike(O);
- aCallable(callbackfn);
- if (length === 0 && argumentsLength < 2) throw new $TypeError(REDUCE_EMPTY);
- var index = IS_RIGHT ? length - 1 : 0;
- var i = IS_RIGHT ? -1 : 1;
- if (argumentsLength < 2) while (true) {
- if (index in self) {
- memo = self[index];
- index += i;
- break;
- }
- index += i;
- if (IS_RIGHT ? index < 0 : length <= index) {
- throw new $TypeError(REDUCE_EMPTY);
- }
- }
- for (;IS_RIGHT ? index >= 0 : length > index; index += i) if (index in self) {
- memo = callbackfn(memo, self[index], index, O);
- }
- return memo;
- };
- };
-
- module.exports = {
- // `Array.prototype.reduce` method
- // https://tc39.es/ecma262/#sec-array.prototype.reduce
- left: createMethod(false),
- // `Array.prototype.reduceRight` method
- // https://tc39.es/ecma262/#sec-array.prototype.reduceright
- right: createMethod(true)
- };
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